一整天我都在试图弄清楚如何让我的解析器工作，但由于某种原因，我总是得到一个 NullPointerException，这是我的代码：
主要活动：
public class MainActivity extends Activity {
XMLHandler data;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
try {
Log.i("PARSER", "versuch!");
/**
* Create a new instance of the SAX parser
**/
SAXParserFactory saxPF = SAXParserFactory.newInstance();
SAXParser saxP = saxPF.newSAXParser();
XMLReader xmlR = saxP.getXMLReader();
URL url = new URL("my xml file"); // URL of the XML
/**
* Create the Handler to handle each of the XML tags.
**/
data = new XMLHandler();
xmlR.setContentHandler(data);
xmlR.parse(new InputSource(url.openStream()));
} catch (Exception e) {
System.out.println(e);
Log.i("PARSER", "ES KLAPPT NICHT!");
}
TextView txt1 = (TextView) findViewById(R.id.txtview1);
txt1.setText(data.getTournament().get(0).get(0).getTeam1().toString());
}
XML处理程序：
public class XMLHandler extends DefaultHandler {
private Tournament tournament;
private TournamentDay currentDay;
private Match currentMatch;
private StringBuilder builder;
@Override
public void endElement(String uri, String localName, String qName)
throws SAXException {
if (qName.equalsIgnoreCase("team1"))
currentMatch.setTeam1(builder.toString());
else if (qName.equalsIgnoreCase("team2"))
currentMatch.setTeam2(builder.toString());
else if (qName.equalsIgnoreCase("resultfinal"))
currentMatch.setResultfinal(builder.toString());
else if (qName.equalsIgnoreCase("result1"))
currentMatch.setResult1(builder.toString());
else if (qName.equalsIgnoreCase("result2"))
currentMatch.setResult2(builder.toString());
else if (qName.equalsIgnoreCase("venue"))
currentMatch.setVenue(builder.toString());
else if (qName.equalsIgnoreCase("gmt"))
currentMatch.setGmt(builder.toString());
else if (qName.equals("match"))
currentDay.add(currentMatch);
else if (qName.equals("day"))
tournament.add(currentDay);
}
@Override
public void startElement(String uri, String localName, String qName,
org.xml.sax.Attributes attributes) throws SAXException {
if (qName.equals("data")) {
tournament = new Tournament();
}
if (qName.equals("day")) {
currentDay = new TournamentDay();
}
else if (qName.equals("match")) {
currentMatch = new Match();
}
else {
builder = new StringBuilder();
}
}
@Override
public void characters(char[] chars, int start, int length) throws SAXException {
builder.append(chars, start, length);
}
public Tournament getTournament() {
return tournament;
}
}
比赛：
public class Tournament {
private List<TournamentDay> days;
public Tournament() {
this.days = new ArrayList<TournamentDay>();
}
public void add(TournamentDay day) {
days.add(day);
}
public TournamentDay get(int i) {
return days.get(i);
}
}
匹配：
public class Match {
private String team1;
private String team2;
private String resultfinal;
private String result1;
private String result2;
private String date;
private String venue;
private String gmt;
public String getTeam1() {
return team1;
}
public void setTeam1(String team1) {
this.team1 = team1;
}
public String getTeam2() {
return team2;
}
public void setTeam2(String team2) {
this.team2 = team2;
}
public String getResultfinal() {
return resultfinal;
}
public void setResultfinal(String resultfinal) {
this.resultfinal = resultfinal;
}
public String getResult1() {
return result1;
}
public void setResult1(String result1) {
this.result1 = result1;
}
public String getResult2() {
return result2;
}
public void setResult2(String result2) {
this.result2 = result2;
}
public String getDate() {
return date;
}
public void setDate(String date) {
this.date = date;
}
public String getVenue() {
return venue;
}
public void setVenue(String venue) {
this.venue = venue;
}
public String getGmt() {
return gmt;
}
public void setGmt(String gmt) {
this.gmt = gmt;
}
}
最后是我的 XML 文件：
<data>
<day>
<match>
<team1>ind</team1>
<team2>afg</team2>
<resultfinal></resultfinal>
<result1></result1>
<result2></result2>
<date>19.09</date>
<venue>1</venue>
<gmt>14:00</gmt>
</match>
<match>
<team1>eng</team1>
<team2>afg</team2>
<resultfinal></resultfinal>
<result1></result1>
<result2></result2>
<date>21.09</date>
<venue>1</venue>
<gmt>14:00</gmt>
</match>
<match>
<team1>ind</team1>
<team2>eng</team2>
<resultfinal></resultfinal>
<result1></result1>
<result2></result2>
<date>23.09</date>
<venue>2</venue>
<gmt>10:00</gmt>
</match>
</day>
<day>
<match>
<team1>aust</team1>
<team2>irl</team2>
<resultfinal></resultfinal>
<result1></result1>
<result2></result2>
<date>19.08</date>
<venue>1</venue>
<gmt>10:00</gmt>
</match>
<match>
<team1>aust</team1>
<team2>west</team2>
<resultfinal></resultfinal>
<result1></result1>
<result2></result2>
<date>22.09</date>
<venue>1</venue>
<gmt>14:00</gmt>
</match>
<match>
<team1>west</team1>
<team2>irl</team2>
<resultfinal></resultfinal>
<result1></result1>
<result2></result2>
<date>24.09</date>
<venue>1</venue>
<gmt>14:00</gmt>
</match>
</day>
</data>
这是日志猫：
09-17 15:26:49.299: I/System.out(3392): java.lang.NullPointerException
09-17 15:26:49.299: I/PARSER(3392): ES KLAPPT NICHT!
09-17 15:26:49.299: D/AndroidRuntime(3392): Shutting down VM
09-17 15:26:49.299: W/dalvikvm(3392): threadid=1: thread exiting with uncaught exception (group=0xb40a64f0)
09-17 15:26:49.299: I/Process(3392): Sending signal. PID: 3392 SIG: 9
09-17 15:26:49.299: D/AndroidRuntime(3392): procName from cmdline: com.example.xmldownloader
09-17 15:26:49.299: E/AndroidRuntime(3392): in writeCrashedAppName, pkgName :com.example.xmldownloader
09-17 15:26:49.299: D/AndroidRuntime(3392): file written successfully with content: com.example.xmldownloader StringBuffer : ;com.example.xmldownloader
09-17 15:26:49.299: E/AndroidRuntime(3392): FATAL EXCEPTION: main
09-17 15:26:49.299: E/AndroidRuntime(3392): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.xmldownloader/com.example.xmldownloader.MainActivity}: java.lang.NullPointerException
09-17 15:26:49.299: E/AndroidRuntime(3392): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1698)
09-17 15:26:49.299: E/AndroidRuntime(3392): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1726)
09-17 15:26:49.299: E/AndroidRuntime(3392): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
09-17 15:26:49.299: E/AndroidRuntime(3392): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:949)
09-17 15:26:49.299: E/AndroidRuntime(3392): at android.os.Handler.dispatchMessage(Handler.java:99)
09-17 15:26:49.299: E/AndroidRuntime(3392): at android.os.Looper.loop(Looper.java:130)
09-17 15:26:49.299: E/AndroidRuntime(3392): at android.app.ActivityThread.main(ActivityThread.java:3770)
09-17 15:26:49.299: E/AndroidRuntime(3392): at java.lang.reflect.Method.invokeNative(Native Method)
09-17 15:26:49.299: E/AndroidRuntime(3392): at java.lang.reflect.Method.invoke(Method.java:507)
09-17 15:26:49.299: E/AndroidRuntime(3392): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:880)
09-17 15:26:49.299: E/AndroidRuntime(3392): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:638)
09-17 15:26:49.299: E/AndroidRuntime(3392): at dalvik.system.NativeStart.main(Native Method)
09-17 15:26:49.299: E/AndroidRuntime(3392): Caused by: java.lang.NullPointerException
09-17 15:26:49.299: E/AndroidRuntime(3392): at com.example.xmldownloader.MainActivity.onCreate(MainActivity.java:58)
09-17 15:26:49.299: E/AndroidRuntime(3392): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
09-17 15:26:49.299: E/AndroidRuntime(3392): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1662)
09-17 15:26:49.299: E/AndroidRuntime(3392): ... 11 more
有人可以帮我吗？或者指出，我做错了什么？谢谢你。